These answers are according to Wikipedia. If it's wrong please let me know.
Winner and Runner-Ups in the Bottom Three:
Season 1: Justin Guarini on 7/31/2002
Season 2: Ruben Studdard on 4/30/2003
Season 3: Fantasia Barrino on 4/21 and 5/12/2004 and Diana DeGarmo on 3/24, 4/07, and 4/15/2004
Season 4: Bo Bice on 4/13/2005
Season 5: Katharine McPhee on 3/29 and 5/10/2006
Season 6: Blake Lewis on 4/18/2007
Season 7: Neither David Cook or David Archuleta were in the bottom three during January 15 - May 21, 2008.
Season 8: Kris Allen and Adam Lambert on 4/29/2009
Season 9: Neither Crystal Bowersox or Lee Dewyze were in the bottom three during January 12 - May 26, 2010.
http://en.wikipedia.org/wiki/American_Idol